A drone strike near the Islamic State terrorist group's (IS or ISIS) de facto Syrian capital Raqa killed a jihadist commander heading to Aleppo province on orders from the organisation's chief, a monitoring group said Thursday.
His death is the latest in a series of blows to the jihadist group in recent weeks, and comes days after Russian-backed Syrian government forces recaptured the ancient city of Palmyra from its grip.
Abu al-Hija, a high-ranking Tunisian ISIS commander, was killed late on Wednesday in a strike by a drone that was "most likely operated by the US-led coalition", the Syrian Observatory for Human Rights said.
He had traveled to Syria from Iraq just 24 hours earlier at the behest of ISIS chief Abu Bakr al-Baghdadi, the Britain-based monitoring group said.
Abu al-Hija is the latest senior ISIS member to be killed in recent weeks.
"IS's leadership is being debilitated," Observatory director Rami Abdel Rahman told AFP.
"Without infiltration of IS, these killings would not have been possible."
The latest killing came after Syrian government troops backed by Russian forces seized Palmyra on Sunday.
The recapture of Palmyra, known as the "Pearl of the Desert" for its colonnaded alleyways and stunning temples, was seen as the biggest blow so far in the war against ISIS in Syria.
While Russia and the United States back opposing sides in the conflict between the Syrian government and rebels, both are intent on crushing the jihadists.
"It is clear that Russia and the United States are coordinating in the fight against IS," Abdel Rahman said.
Abu al-Hija had been ordered by Baghdadi to travel from Iraq to Aleppo province near Turkey's border, to oversee ISIS resistance to an offensive by US-backed fighters of the Kurdish-led Syrian Democratic Forces.
"The fighting, which has been especially fierce in the past four or five days, could lead to IS being expelled from the area and pushed eastwards into Raqa province," Abdel Rahman said.
A top Pentagon official said earlier this week that IS was losing the fight against the US-led coalition in both Syria and Iraq, even as it continues to mount attacks overseas, like the suicide bombings that killed 35 people in Brussels on March 22.
AFP contributed to this report.